JPH03281959A - Electronically controlled fuel injection device for internal combustion engine - Google Patents

Abstract

PURPOSE:To effectively prevent an engine from being lowered in revolution after it has been started by resetting an increment correction factor to an increasing side after the engine has been started when the engine is lowered in revolution to the value less than a specified one for the definite time after the engine has been started, and accordingly resetting a decrement value to the increasing side. CONSTITUTION:An electronically controlled fuel injection device for an internal combustion engine is equipped with an after starting increment correction factor setting means (a) which sets up an after starting increment correction factor in such a way that the correction factor is gradually decreased from the initial value set up in response to engine temperature by a decrement set in response to the initial value with time for the definite period of time after the engine has been started, and is also equipped with an after starting increment correction means (b) which makes incremental correction for the quantity of fuel injection based on the aforesaid after starting increment correction factor. In this case, a revolution reduction detecting means (c) is provided, which detects that the engine is lowered in revolution to the value less than a specified one for the definite period of time, and an after starting increment correction factor resetting means is also provided, which resets the after starting increment correction factor to the increasing side of the after starting increment correction factor when an reduction in revolution is detected. In addition, a decrement value resetting means (e) is also provided, which resets the decrement value to the increasing side.

Description

DETAILED DESCRIPTION OF THE INVENTION <Industrial Application Field> The present invention relates to an electronically controlled fuel injection device for an internal combustion engine, and particularly relates to a technique for increasing the amount of fuel injection after startup.

<Prior art> Conventionally, in electronically controlled fuel injection systems for internal combustion engines, the basic fuel injection amount is set based on the intake air flow rate and the engine speed, and corrections are made to this according to the engine operating status. ,
The amount of fuel injected by the fuel injection valve is set.

Here, as one of the above-mentioned corrections, there is a post-start increase correction, which is constant after the engine starts (after the start switch ST/SW is switched from ON to OFF) as shown in Fig. 7. As shown in the map of FIG. 8, the initial value M K
A post-start increase correction coefficient KAs is set by gradually decreasing over time by a gradual decrease value set according to As, and the fuel injection amount is increased by the post-start increase correction coefficient.

<Problems to be Solved by the Invention> By the way, the above-mentioned map is set to be compatible with standard gasoline, so gasoline with low vapor pressure (summer gasoline), which is less likely to evaporate than standard gasoline, can be used at different temperatures. When used in winter when temperatures are low, a large amount of the fuel injected from the fuel injector does not vaporize and adheres to the walls of the intake manifold, causing a delay in reaching the combustion chamber. There were problems such as the engine becoming lean and causing a drop in rotation after starting (see X in Figure 7).

SUMMARY OF THE INVENTION In view of the above-mentioned problems, it is an object of the present invention to provide an electronically controlled fuel injection system for an internal combustion engine that does not suffer from rotation drop after startup.

<Means for Solving the Problems> In order to achieve the above object, the present invention, as shown in FIG. Post-starting increase correction coefficient setting means (a) for setting a post-starting increase correction coefficient by gradually decreasing over time by a gradual decrease value set according to the value;
and a post-start increase correction means (b) for increasing the fuel injection amount based on the post-start increase correction coefficient, the following (C) to (e) are provided.
).

(C) Rotation reduction detection means for detecting a decrease in the engine rotation speed to a predetermined value or less during the certain period of time @ When the rotation reduction is detected, the post-start increase correction is performed to increase the post-start increase correction coefficient at that time. Post-start increase correction coefficient resetting means (e) for resetting the coefficient Gradual decrease value resetting means for resetting the gradual decrease value to the increasing side when resetting the post-start increase correction coefficient <Operation> According to the above configuration, The following effects can be obtained.

An initial value is set according to the engine temperature, a gradual decrease value is set according to this initial value, and the increase correction coefficient after startup is set by gradually decreasing from the initial value by the gradual decrease value over time.

Based on this post-start increase correction coefficient, the fuel injection amount is corrected to increase.

If a drop in the engine speed below a predetermined value is detected during a certain period of time after startup (during increase correction), the post-start increase correction coefficient is reset to increase to prevent rotation drop. In addition, even if the gradual decrease value is reset to the increasing side and the increase correction coefficient after startup is increased, the gradual decrease speed is increased correspondingly so that the increase correction time does not change significantly.

<Example> An example of the present invention will be described below based on FIGS. 2 to 6.

First, the system will be explained with reference to FIG.

Air is taken into the engine 1 from an air cleaner 2 through an intake duct 3, a throttle valve 4, and an intake manifold 5.

A fuel injection valve 6 is provided in a branch portion of the intake manifold 5 for each cylinder.

The fuel injection valve 6 is an electromagnetic fuel injection valve that opens when the solenoid is energized and closes when the energization is stopped. Fuel is injected and supplied from the fuel pump and adjusted to a predetermined pressure by the pressure regulator.

The combustion chamber of the engine 1 is provided with an ignition plug 7, which ignites a spark to ignite and burn the air-fuel mixture.

The control unit 12 includes a CPU and a ROM.

It is equipped with a microcomputer including a RAM and an input/output interface, receives input signals from various sensors, performs arithmetic processing as described later, and controls the operation of the fuel injection valve 6.

As the various sensors mentioned above, a hot wire type air flow meter 13 is provided in the intake duct 3 to detect the intake air flow rate Q.

Further, a crank angle sensor 14 is provided, and in the case of a four-cylinder engine, outputs a reference signal for every crank angle of 180' and a unit signal for every crank angle of 1 to 2 degrees.

Here, the engine speed N can be calculated by measuring the cycle of the reference signal or the number of unit signals generated within a predetermined time.

Further, a water temperature sensor 15 is provided facing the water jacket of the engine 1 to detect the cooling water temperature Tw. From this you can know the engine temperature.

Further, an ON/OFF signal from the start switch 17 is output.

Here, the CPU of the microcomputer built in the control unit 12 executes the programs (fuel injection amount setting routine, first post-start increase correction coefficient setting routine, second According to the post-start increase correction coefficient setting routine),
Performs calculation processing and controls fuel injection amount.

First, the fuel injection amount setting routine will be explained with reference to the flowchart shown in FIG.

In step 1 (denoted as 81 in the figure; the same applies hereinafter), the intake air flow rate Q and the engine speed N are input.

In step 2, the basic fuel injection amount TP is set according to the following formula.

Tp=to-Q/N; constant step 3
Then, the correction coefficient C0EF that includes □ in the starting increase correction coefficient
is set according to the following formula.

C0EF=4+Kyw+Ksy+KAs+ "'; 71 is a water temperature correction coefficient, and KST is a start-up increase correction coefficient. In step 4, a voltage correction numerator s is set in accordance with the battery voltage.

In step 5, the fuel injection amount Ti is set using the correction coefficient C0EF and the like according to the following equation.

Ti=Tp -C0EF+Ts Here, steps 3 and 5 correspond to the start-up increase correction coefficient.

Then, a signal with a pulse width corresponding to the fuel injection amount Ti is
The fuel is output to the fuel injection valve 6 at a predetermined timing synchronized with the rotation of the engine.

Next, the first post-start increase correction coefficient setting routine will be described with reference to the flowchart in FIG.

In addition, FIG. 6 shows the switching timing of the start switch (ST/5W) 17 and the post-start increase correction coefficient KA.

and the control characteristics of the engine speed N.

In step 11, the start switch 17 is turned on and off.
Determine F.

When ON (during startup), proceed to step 12, substitute 0 for the post-start increase correction coefficient Kas, and then proceed to step 1.
Proceed to step 3, reset the reset flag F, and end this routine.

On the other hand, if it is determined in step 11 that the start switch 17 is OFF (after starting), the process proceeds to step 14 and the
It is determined whether it is immediately after switching from N to OFF.

Immediately (YES), proceed to step 15, and based on the cooling water temperature Tw detected by the water temperature sensor 15, refer to the map and set the initial value M of the post-start increase correction coefficient KAS.
Search for Kas.

In step 16, a gradual decrease value DKa of the increase correction coefficient after startup is determined.
S is set according to the following formula.

DKA! "MKAS/CmaX; Ctaax is a constant amount increase time after start-up. In step 17, the initial value M K As is substituted for the after-start increase correction coefficient KA3.

As a result, the post-start increase correction is started, and the fifth
According to the flowchart in the figure, the post-start increase correction coefficient KAS is gradually decreased as time passes.

On the other hand, if the determination in step 14 is that the start switch 17 is not immediately after being switched from ON to OFF (NO), the process proceeds to step 18, where it is determined whether the reset flag F is set.

If not, the process proceeds to step 19, where it is determined whether the engine speed N is less than a predetermined value A and the amount of change ΔN in the engine speed is negative (<O) (during descent).

Note that this judgment condition is for detecting a drop in engine speed, but the judgment condition is also set as a range of cooling water temperature where a drop in engine speed is likely to occur due to two-way gasoline properties.
May be added.

When YES, that is, when N≦A and ΔN×O,
Since a rotation drop has occurred, proceed to step 20 and add a certain amount A to the post-start increase correction coefficient KA at that time.
KAs is added and the post-start increase correction coefficient is reset to 0 according to the following formula.

K a s = K As + A K As In step 21, the gradual decrease value DKAs is reset according to the following formula.

D K As -K as/ (Cwax C) Here, C is the elapsed time after startup (the time counter value measured in step 33 in FIG. 5, which will be described later), and Csaχ
-C indicates the remaining time of the constant post-start increase time Cyaax during which the post-start increase correction is performed.

The reason for resetting the gradual decrease value DKAs is to increase the gradual decrease speed so that the increase time does not change even if the post-start increase correction coefficient KA is reset and becomes larger.

In step 22, the reset flag F is set, and this routine ends.

On the other hand, if the resetting flag F has already been set in step 18, and if the determination in step 19 is NO, this routine is terminated. , step 20 corresponds to a post-start increase correction coefficient resetting means, and step 21 corresponds to a gradual decrease value resetting means.

Next, the second post-start increase correction coefficient setting routine executed every unit time will be explained with reference to the flowchart of FIG.

In step 31, start switch (ST/5W) 1
7 is determined to be 0N-OFF.

When it is ON, the process proceeds to step 32, where the time counter value C is set to 0, and this routine is ended.

On the other hand, if it is determined in step 31 that the start switch 17 is OFF, the process proceeds to step 33, where 1 is added to the time counter value C, and the process proceeds to step 34.

In step 34, the time counter value C is compared with the post-start fuel increase time CIIIax, and when the counter value C is less than the post-start fuel increase time Cmax, the process proceeds to step 35.
Set the post-start increase correction coefficient KAs according to the following formula,
Exit this routine.

K As= K As D Kas Here, step 35 corresponds to the post-start increase correction coefficient setting means.

Moreover, when C≧Cwax, this routine is ended as it is.

At this time, since the post-start device correction coefficient KAS is 0, no increase correction is made.

The reason for keeping the increase time constant is that the time required for the engine to stabilize at idle is approximately constant, and that changing this time will affect other controls.

<Effects of the Invention> As explained above, according to the present invention, when the engine speed drops below a predetermined value during a certain period of time after the engine is started, the post-start increase correction coefficient is reset to increase; Additionally, since the gradual decrease value is reset to the increasing side, it is possible to effectively prevent rotational drop after startup.

[Brief explanation of drawings]

The first view is a functional block diagram showing the configuration of the present invention, the second is a system diagram of an embodiment of the present invention, the third is a flowchart of the fuel injection amount setting routine, and the fourth is the increase correction after the first start. The flowchart of the coefficient setting routine, Figure 5 is the second
A flowchart of the post-start correction coefficient setting routine, Fig. 6 is a diagram showing control characteristics, Fig. 7 is a diagram showing conventional control characteristics, and Fig. 8 is a diagram showing the relationship between cooling water temperature and the initial value of the post-start increase correction coefficient. It is a line diagram showing a relationship. 1... Engine 6... Fuel injection valve 12... Control unit 13... Air flow meter
14...Crank angle sensor 15...Water temperature sensor 17...Start switch

Claims (1)

[Claims] For a certain period of time after the engine is started, from the initial value set according to the engine temperature, by a gradual decrease value set according to the initial value,
An internal combustion engine having a post-start increase correction coefficient setting means for setting a post-start increase correction coefficient by gradually decreasing it over time, and a post-start increase correction coefficient for increasing the fuel injection amount based on the post-start increase correction coefficient. In the electronically controlled fuel injection system, the engine speed decrease detection means detects a decrease in the engine speed to a predetermined value or less during the certain period of time, and when the rotation decrease is detected, the current post-start increase correction coefficient is increased. a post-start increase correction coefficient resetting means for resetting the post-start increase correction coefficient; and a gradual decrease value resetting means for resetting the gradual decrease value to an increasing side when resetting the post-start increase correction coefficient. An electronically controlled fuel injection device for an internal combustion engine, characterized in that: